Microplastics Found 2,000 Meters Deep in Hydrothermal Vent Animals

Plastic pollution is increasingly recognized as a planet-wide stressor rather than a problem confined to coasts. Researchers estimate that roughly 11 million tons of plastic enter the oceans every year, where large debris gradually fragments into microplastics. These microscopic particles can be dispersed by ocean currents across vast distances, raising concerns about bioaccumulation and eventual transfer through marine food webs.

Most previous work has focused on surface waters and coastal regions. Yet nearly 90% of Earth’s ocean volume lies in the deep sea, a realm that is largely inaccessible for routine monitoring. In that environment, hydrothermal vent ecosystems are especially compelling: they host complex communities driven by chemical energy instead of sunlight, while remaining among the most remote habitats on the planet.

In a comparative study, scientists led by Dr. Se-Joo Kim and Dr. Jinyoung Jeong at the Korea Research Institute of Bioscience and Biotechnology (KRIBB), together with colleagues from the Korea Institute of Ocean Science and Technology (KIOST), investigated how microplastics accumulate in vent-dwelling animals from two different ocean basins. Deep-sea snails and mussels were collected from vents over 2,000 meters deep in the North Fiji Basin (southwestern Pacific Ocean) and the Central Indian Ridge (Indian Ocean).

Microplastics were detected in 92% of the analyzed animals, with an average of 3.42 particles per individual. Among the polymer types observed, polystyrene—common in consumer and packaging materials—was the most abundant, indicating that widely used plastics are reaching even chemically extreme deep habitats.

The team found that biology strongly shapes microplastic distribution inside organisms. In grazing snails that feed on microbial mats, microplastics concentrated mainly in digestive organs. In contrast, filter-feeding mussels showed a more uniform spread across tissues, consistent with different ingestion pathways.

Regional conditions also mattered. After accounting for body weight, microplastic concentrations in the Indian Ocean were up to 14.7 times higher than in the southwestern Pacific. The authors propose that differences in riverine plastic inputs, human activity, and large-scale circulation patterns likely contribute to this disparity.

Overall, the results provide direct evidence that pollution generated at the ocean surface can be transported thousands of meters downward. The findings imply that future deep-sea assessments will need to consider both hydrodynamic transport and species-specific feeding strategies to accurately predict contamination risk.

The study, published online June 3 in Water Research, supports the development of deep-sea monitoring frameworks, informs environmental impact assessments for deep-sea mineral resource development, and strengthens conservation priorities for vent ecosystems.

Keywords

microplastics; hydrothermal vents; bioaccumulation; deep sea; polystyrene; feeding strategy; Indian Ocean; southwestern Pacific